Surgical instrument

ABSTRACT

The invention relates to an instrument for surgery, in particular minimally invasive surgery. The instrument includes means for feeding back a force which is exerted on the working element of the instrument to the operating element. These means include at least a first force sensor for measuring the force which is exerted on the working element, a control unit and a first actuator. On the basis of a signal which originates from the first force sensor, the control unit controls at least the first actuator in order to control the operating element. Furthermore, the means preferably include a first position sensor for measuring a position of the working element with respect to the frame. The control unit advantageously determines an impedance which the working element is subject to as a result of the presence of a tissue or the like, on the basis of which impedance the control unit controls at least the first actuator.

TECHNICAL FIELD OF THE INVENTION

The present invention relates to an instrument for surgery, inparticular minimally invasive surgery, which instrument comprises anelongate frame which, in the vicinity of a first end thereof, comprisesan operating element, which can be operated manually, and, at a secondend thereof, at least one working element which can move with respect tothe frame.

DESCRIPTION OF RELATED ART

An instrument of this type is used in particular in surgical procedureswhich use minimally invasive operating techniques. In a minimallyinvasive operation of this type, a number of small incisions are madeand instruments and the like can be inserted through these incisions.Generally, a cylindrical tube is placed into the incision and theinstruments are placed through it. The instruments which are used inprinciple correspond to the instruments which are used in conventionaloperating techniques. However, a narrow and elongate instrument isrequired in order to satisfy the specific requirements of the minimallyinvasive method, i.e. the instrument has to be placed through therelatively narrow tube, the working element projecting at one end of thetube while the operating element projects at the other end of the tube.A suitable instrument therefore comprises at least one elongate frame, aworking element which can move with respect to the frame and anoperating element, by means of which the working element of theinstrument can be operated. The working element of the instrument mayhave various functions. For example, it can be used to clamp, grip, cutor staple. In cases which require a plurality of actions or instruments,two or more working elements which can move with respect to the framewill be used.

Minimally invasive operating techniques have the advantage that asmaller incision is required, and consequently there is generally lessrisk of infection and on average a shorter hospitalization is required.

In addition to the known benefits of the minimally invasive operatingtechniques, a number of drawbacks should also be mentioned. The surgeondoes not have a direct view of the actions which he is carrying out. Itis necessary to use cameras and television screens or the like to obtainthe visual information which is directly available to him inconventional operating techniques. The specific shape of theinstruments, i.e relatively narrow and elongate, which are used resultin more friction in relative terms, and the instruments are moreflexible, with the result that the mechanical feedback of the forceexerted on the working element to the operating mechanism is less good.Consequently, the surgeon has less idea of the force which he isexerting by means of the working element of the instrument on somethingwhich is in the working element of the instrument. Consequently, it ispossible, for example, that he may damage tissue as a result of clampingit too hard.

WO 98/11833 discloses an instrument for minimally invasive operatingtechniques in which the friction in the instrument is reduced comparedto conventional designs through the use of rolling-contact bearings.This results in an improved mechanical feedback of the force which isexerted on the working element of the instrument. However, on account ofthe specific shape required for instruments for minimally invasivesurgery, friction and hysteresis are still present in the design, andconsequently the force which is exerted on the working element of theinstrument is not correctly fed back to the operating mechanism of theinstrument. As a result, the user of an instrument of this type does nothave an optimum “feeling” for the tissue or the like which he ismanipulating with the instrument. It is then difficult for a surgeon toposition the working element of the instrument accurately.

The object of the invention is to provide an improved instrument for usein surgery, in particular minimally invasive surgery, which eliminatesthe above-mentioned drawback.

SUMMARY OF THE INVENTION

The object is achieved with an instrument according to the preamble ofclaim 1, characterized in that the instrument comprises means forfeeding back a force which is exerted on the working element of theinstrument to the operating element, which means comprise at least afirst force sensor for measuring the force which is exerted on theworking element, a control unit and a first actuator which is coupled tothe operating element, the control unit controlling at least the firstactuator on the basis of a signal which originates from the first forcesensor.

By measuring the force which is exerted on the working element using aforce sensor and feeding it back via a control unit to the operatingelement, the user can feel the force which is exerted by the workingelement without this feeling being influenced by friction and/orhysteresis in the instrument. The operating element is then, as it were,controlled by the first actuator.

The working element used in the instrument may have various functions.For example, it may be suitable for clamping, gripping, pinching orstapling or for holding a needle or the like. Often, there are two ormore of these working elements which can move with respect to the frame.Furthermore, the instrument may be designed in such a manner that theworking elements can be positioned exchangeably in the instrument.

The operating element is operated manually and is generally an operatinghandle as is present in a conventional surgical instrument. However, itis also possible for the operating element to be designed differently,for example as a rotary button or the like.

The surgical instrument is preferably to be held by hand.

The sensors, actuators and the control unit are preferably integrated inthe instrument or secured directly to the instrument. As a result, theinstrument remains easy to handle, so that the user finds it easy to useand can be very flexible in his movements. The instrument according tothe invention can be designed advantageously with dimensionssubstantially corresponding to the dimensions of conventional minimallyinvasive instruments or an only slightly enlarged version thereof.

Preferably, the control unit determines an impedance to which theworking element is subject, for example as a result of the presence of atissue or the like, on the basis of the force which is exerted on theworking element, the position in which the working element is locatedwith respect to the frame and the speed at which the working element ismoving with respect to the frame, the control unit controlling at leastthe first actuator on the basis of the impedance.

The impedance of a specific material is a good measure of the feelingprovided by a material of this type when it is touched. The control unitaccording to the invention advantageously feeds the impedance to whichthe working element of the instrument is subject back to the operatingelement, so that the user has a very realistic “feeling” of the tissueor the like which is being manipulated by the working element.

The force which is exerted on the working element and the position ofthe working element with respect to the frame are determined with theaid of the first force sensor and first position sensor respectively.The speed of the working element is preferably determined by thederivative over the course of time of the position signal measured bythe first position sensor, but it is also possible, by way of example,to determine the speed using a separate speed sensor.

In a preferred embodiment, the instrument has a connecting rod or thelike which is coupled to the working element and to the operatingelement in order to drive the working element.

This results in what is known as a semi-active instrument, in which theworking element at the end of the frame is driven directly, i.e. via amechanical connection, by the surgeon, while the control unit uses thefirst actuator to control the operating element on the basis of thedetected impedance.

In another preferred embodiment, the instrument has a connecting rod orthe like which is coupled to the working element in order to drive theworking element, the connecting rod or the like being driven by a secondactuator which is controlled by the control unit.

In what is known as a fully active instrument of this type, the controlsof the operating movements of the surgeon and the movement of theworking element pass via the control unit. The control unit controls thetwo actuators on the basis of signals which are obtained from the forceand position sensors.

The control unit preferably determines an impedance to which theoperating element is subject on the basis of the force which is exertedon the operating element, the position and speed of the operatingelement, which impedance is likewise fed back to the actuators. In thisway, the feedback of feeling is improved still further. In this case,the force on the operating element and the position of the operatingelement are measured by means of a second force sensor and positionsensor, respectively. The speed is preferably determined as a derivativeover the course of time of the position signal measured by the secondposition sensor.

Advantageously, at least one of the force sensors and/or positionsensors comprises a glass fibre, whereby a light source and a lightsensor are positioned in the vicinity of a first end of the glass fibre,and whereby a reflective surface, which moves as a function of theposition and/or force which is to be measured, is arranged at a distancefrom a second end of the glass fibre. The force and/or position sensorsmake use of glass fibres and reflective surfaces; the extent to whichlight which originates from the light source and emerges from the secondend of the glass fibre is reflected into the second end of the glassfibre being representative of the force or position which is to bemeasured. The amount of light which is reflected is in this casedetected by the light sensor.

Sensors of this type have the advantage over more conventional sensorsin that no electrical signals are used at least in the vicinity of theworking element. The use of electrical signals is undesirable, since themeasurement signals from the sensors may be interfered with by otherequipment present in the operating theater. Moreover, glass fibres areinexpensive and take up little space.

In a force sensor, the second end of the glass fibre and the reflectivesurface are fixed to the working element. A force exerted on the workingelement will cause this working element to bend slightly or change itsshape in some other way. This bending or other change in shape willchange the position and/or orientation of the reflective surface withrespect to the second end of the glass fibre. As a result, the extent towhich light which emerges from the second end of the glass fibre isreflected into the second end of the glass fibre will change. The forceexerted on the working element can be determined on the basis of thischange in the amount of light which is reflected.

The position of the working element can be determined in a correspondingway using a position sensor. In a position sensor, of this type,however, the second end of the glass fibre is not arranged on theworking element, but rather on the frame, so that the level ofreflection depends on the position of the working element with respectto the frame.

As an alternative to glass fibres, incidentally, it is also possible touse other suitable light conductors.

Advantageously, the instrument comprises at least two parts which can bedetached from one another, of which one part is suitable for reuse,generally after sterilization, and another part is suitable for singleuse, which two parts can be coupled to one another by means of acoupling.

The use of glass fibres makes the instrument as a whole more difficultto sterilize, since the glass fibres are damaged by heating. However,making the instrument disposable makes use of the instrument veryexpensive, on account of the electronics required for the control unitand the light sensor(s) and the actuators. By separating the expensivecomponents, in particular electronics and actuators, of the instrumentfrom the section of the instrument in which the glass fibres run, it ispossible for the instrument to be kept in use reliably andinexpensively.

A particular advantage is that with the instrument it is possible torecord data which are measured by the various sensors. Data of this typemay be important for the development of computer models which are used,for example, in simulation training exercises or the like. For thispurpose, a surgical simulator comprises an operating element which canbe operated manually, a first actuator for controlling the operatingelement by means of a force, and control means which are designed tocontrol the first actuator on the basis of an impedance from an actualsurgical procedure carried out using an instrument as described above.The use of the instrument according to the invention in a specificsurgical intervention can therefore be practiced by simulating theworking element and the forces exerted on it with the aid of the controlmeans. In this case, the first actuator can be controlled in the sameway as if it were being controlled by the control unit of theinstrument, and the above-mentioned second force sensor and secondposition sensor can also be used in corresponding ways. Also, theoperating section of the instrument can be used in a telesurgeryinstrument, comprising an operating element which can be operatedmanually, a first actuator for controlling the operating element bymeans of a force, and control means which are designed to control thefirst actuator on the basis of an impedance from a surgical procedurecarried out remotely. In this case too, the first actuator can becontrolled in the same way as if it were being controlled by the controlunit of the instrument, and the above-mentioned second force sensor andsecond position sensor can also be used in a corresponding way.

Furthermore, the invention relates to a force sensor in accordance withclaim 18 and to a position sensor in accordance with claim 19. Preferredembodiments of the force sensor and position sensor can be designed inaccordance with the ways which have been explained in more detail forthe force and position sensors for the instrument according to theinvention.

BRIEF DESCRIPTION OF THE DRAWINGS

Further characteristics and advantages of the instrument according tothe invention will be explained in more detail below with reference to anumber of embodiments which are illustrated in the appended drawings, inwhich:

FIG. 1 diagrammatically depicts a first preferred embodiment of aninstrument according to the invention,

FIG. 2 diagrammatically depicts a second preferred embodiment of aninstrument according to the invention,

FIG. 3 diagrammatically depicts a force sensor of an instrumentaccording to the invention, and

FIG. 4 diagrammatically depicts a position sensor of an instrumentaccording to the invention.

Throughout the various figures, the same reference numerals are used torefer to corresponding components or components which have acorresponding action.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

FIG. 1 shows a first preferred embodiment of the instrument according tothe invention, denoted overall by reference numeral 1. The variouscomponents of the instrument 1 are diagrammatically depicted in thefigure. The instrument 1 comprises an elongate frame 2 having, at afirst end, at least one operating element 3 and, at the second end, aworking element 4 which is moveably secured to the frame and a secondworking element 5 which in this case is fixed to the frame and forms acomponent thereof. It is also possible to make a second working elementmoveable with respect to the frame and to provide more than two fixed ormoveable working elements.

A force sensor 6 for measuring the force which is exerted on the workingelement 4 and a position sensor 7 for measuring the position of theworking element 4 with respect to the frame 2 are also arranged in orclose to the working element 4. A force sensor 8 for measuring the forcewhich is exerted on the operating element and a position sensor 9 formeasuring the position of the operating element with respect to theframe are arranged in or close to the operating element 3. The measuredsignals from the force sensors 6, 8 and position sensors 7, 9 aretransmitted to a control unit 10.

The force sensors 6, 8 and position sensors 7, 9 may be conventionalsensors which, by way of example, use strain gauges, potentiometers orthe like. For in particular the sensors which are positioned in or closeto the working element 4, it is preferable to use sensors in which glassfibres are used. Sensors of this type are less sensitive to interferencethan electrical sensors and will be described in more detail below.

The instrument 1 also comprises an actuator 11 which is coupled to theoperating element 3 and an actuator 12 which drives a connecting rod 13to which the working element 4 is coupled. The actuators can becontrolled independently of one another by the control unit. Theactuators are preferably linear electromagnetic actuators.

In the control unit 10, the impedance to which the working element 4 issubject is determined on the basis of the force which is exerted on theworking element 4, the position of the working element 4 and the speedof the working element 4. An impedance to which the operating element issubject is also determined on the basis of the force to which theoperating element is subject, the position of the operating element andthe speed of the operating element. The speeds are in this casecalculated by taking the derivative over time of the signal from theposition sensors. The two actuators 11, 12 are controlled by the controlunit 10 on the basis of the two impedances which have been determined.

The instrument 1 comprises at least two parts which can be detached fromone another, of which a reusable part is suitable for reuse aftersterilization and another, disposable part is suitable for single use.The two parts which can be separated from one another are indicated byline A-A in the figure. The two parts can be coupled to one another bymeans of a coupling. The coupling comprises a mechanical coupling 14 fordriving the connecting rod 13 in the disposable part. There is also anoptical coupling 15 for coupling optical information, i.e coupling theglass fibres in the disposable part to opto-electronic means, such asthe light sensor and the light source.

The reusable part comprises the actuators 11, 12, the control unit 10,the light source, the light sensor, which are preferably accommodated ina watertight housing, so that they are protected from moisture and thelike.

A second preferred embodiment of the instrument according to theinvention is shown in FIG. 2. In this case, the connecting rod 13 isdirectly mechanically coupled to the operating element 3. The forcewhich the user exerts on the operating element 3 is transmitted directlyto the working element 4 via the connecting rod 13. A force sensor 6 anda position sensor 7 are arranged in or close to the working element 4.The signals from the force sensor 6 and the position sensor 7 aretransmitted to a control unit 10 which controls an actuator 11 which iscoupled to operating element 3. The control unit 10 controls theactuator 11, with a view to controlling the operating handle, on thebasis of the impedance which is determined in the control unit by meansof the measured position and force and the calculated speed. As aresult, the user is provided with good feedback about the way in whichhe is manipulating a tissue or the like using the working element.

The instrument 1 is composed of a disposable part and a reusable partwhich comprises a coupling in the region of line A-A. The coupling has amechanical coupling 14 for driving the working element 4 and an opticalcoupling 15 for transmitting optical information.

FIG. 3 shows at least part of a preferred embodiment of the force sensorof the instrument according to the invention, which force sensorcomprises a glass fibre. The figure shows one end of an instrument,where two working elements 4 which can move with respect to the frameand form a clamping jaw, are arranged. The clamping jaw is opened bymoving the connecting rod 13 in the direction of the clamping jaw, andthe clamping jaw is closed by moving the connecting rod 13 away from theclamping jaw. One end of a glass fibre 16 extends at least part way intoone of the working elements 4. A light source and a light sensor(neither of which is shown) are arranged in the vicinity of the otherend of the glass fibre 16. The light source emits light through theglass fibre 16, and the light source detects the light which returnsthrough the glass fibre 16.

In the vicinity of the end of a working element 4 of the clamping jawwhich is remote from the instrument, there is a reflective surface 17which at least partially reflects light which emerges from the end ofthe glass fibre 16 into the glass fibre 16. The reflective surface ispositioned at a set distance from the end of the glass fibre 16. If aforce is then exerted on the working element 4, the working element 4will bend slightly. The result of this bending is that the amount oflight which is reflected by the reflective surface 17 into the glassfibre 16 changes. This change, which is detected by the light sensor, isa measure of the force which is exerted on the working element 4. Theamount of light which is measured is converted by the light sensor intoan electrical signal which is representative of the force exerted on theinstrument. This signal is transmitted to the control unit 10.

FIG. 4 shows at least part of a preferred embodiment of the positionsensor of the instrument according to the invention, which positionsensor comprises a glass fibre 18. The figure shows an end of aninstrument corresponding to FIG. 3. The glass fibre 18 is secured to theframe 2 of the instrument 1. One end is directed towards a reflectivesurface 19 which is secured to one of the working elements 4. The lightwhich is emitted by a light source (not shown) arranged at the other endof the glass fibre is at least partially reflected by the reflectivesurface 19 into the glass fibre 18. If the clamping jaw is moved withrespect to the frame 2, more or less light is reflected into the glassfibre 18. The amount of light which is reflected and which is detectedby the light sensor is a measure of the position of a working element 4of the clamping jaw with respect to the frame 2. On the basis of theamount of light received, the light sensor emits an electrical signal,which is representative of the position of the working elements 4, tothe control unit 10.

1. An instrument for surgery, in particular minimally invasive surgery,said instrument comprising: an elongate frame which, in the vicinity ofa first end thereof, comprises an operating element (3), and, at asecond end thereof, at least one working element (4), characterized inthat the instrument (1) comprises means for feeding back a force whichis exerted on the working element (4) of the instrument to the operatingelement (3), which means comprise at least a first force sensor (6) formeasuring the force which is exerted on the working element, a controlunit (10) and a first actuator (11) which is coupled to the operatingelement, the control unit being configured to control at least the firstactuator (11) on the basis of a signal which originates from the firstforce sensor, wherein the first force sensor (6) comprises a glass fiber(16) configured to guide optical signals to and from the working element(4), whereby a light source and a light sensor are arranged in thevicinity of a first end of the glass fiber, and a second end of theglass fiber is fixed to the working element (4), and whereby areflective surface (17) is arranged on the working element (4) at adefined distance from the second end of the glass fiber, whichreflective surface reflects at least a proportion of the light whichoriginates from the light source and emerges from the second end of theglass fiber into the second end of the glass fiber.
 2. The instrumentaccording to claim 1, characterized in that the instrument (1) has aconnecting rod (13), which is coupled to the working element (4) and tothe operating element (3) in order to drive the working element.
 3. Theinstrument according to claim 1, characterized in that the instrument(1) has a connecting rod (13) which is coupled to the working element(4) in order to drive the working element, the connecting rod beingdriven by a second actuator (12) which is controlled by the control unit(10).
 4. The instrument according to claim 3, characterized in that thecontrol unit (10) determines an impedance to which the operating element(3) is subject on the basis of the force which is exerted on theoperating element, the position in which the operating element islocated with respect to the frame (2) and a speed at which the operatingelement is moving with respect to the frame, the control unitcontrolling the actuators (11, 12) on the basis of the impedance towhich the working element (4) is subject and the impedance to which theoperating element is subject.
 5. The instrument according to claim 3,characterized in that the actuators (11, 12) are electromagnetic linearactuators.
 6. The instrument according to claim 1, characterized in thatthe instrument (1) comprises at least two parts which are detachablefrom one another, of which one part is suitable for reuse and anotherpart is suitable for single use, said two parts being coupleable to oneanother by means of a coupling.
 7. The instrument according to claim 6,characterized in that the coupling comprises a mechanical coupling (14)and an optical coupling (15).
 8. The instrument according to claim 6,characterized in that the part which is suitable for reuse comprises atleast actuators (11, 12), the control unit (10), a light source, a lightsensor and the operating element (3), and in that the part which issuitable for single use comprises at least the working element (4) andglass fibers (16, 18).
 9. The instrument according to claim 8,characterized in that the actuators (11, 12), the control unit (10), thelight source and the light sensor are accommodated in a watertightenclosure.
 10. The instrument of claim 1, wherein the at least oneworking element is moveable with respect to the frame.
 11. Theinstrument of claim 1, wherein the operating element is manuallyoperable.
 12. The instrument according to claim 1, wherein the first endof the glass fiber is located spaced from the working element.
 13. Theinstrument according to claim 1, wherein the means further comprise afirst position sensor (7) configured for measuring a position of theworking element (4) with respect to the frame (2).
 14. The instrumentaccording to claim 13, characterized in that the means further comprisea second force sensor (8) for measuring a force which is exerted on theoperating element (3) and a second position sensor (9) for determining aposition of the operating element with respect to the frame.
 15. Theinstrument according to claim 14, characterized in that at least one ofthe force sensors (6, 8) and position sensors (7, 9) comprises a glassfiber, whereby a light source and a light sensor are positioned in thevicinity of a first end of the glass fiber, and whereby a reflectivesurface, which moves as a function of the position and/or force which isto be measured, is arranged at a distance from a second end of the glassfiber.
 16. The instrument according to claim 13, characterized in thatthe first position sensor (7) comprises a glass fiber (18), whereby alight source and a light sensor are positioned in the vicinity of afirst end of the glass fiber, and a second end of the glass fiber isarranged on the frame, and whereby a reflective surface (17) which ispositioned at a certain distance from the second end of the glass fiberis arranged on the working element (4), which reflective surface (19) atleast partially reflects light which originates from the light sourceand emerges from the second end of the glass fiber into the second endof the glass fiber.
 17. The instrument according to claim 1, wherein thecontrol unit (10) is configured to determine an impedance to which theworking element (4) is subject on the basis of the force which isexerted on the working element, the position in which the workingelement is located with respect to the frame (2), and a speed at whichthe working element is moving with respect to the frame, the controlunit being configured to control at least the first actuator (11) on thebasis of the impedance.
 18. The instrument according to claim 1, whereinthe force exerted on the working element is determined based on a changein the amount of light which is reflected back into said second end ofthe glass fiber.